When looking for historical models for what the next US civil war would look like, there are a number of interesting examples to look at like India and Pakistan during the 1947 partition, Yugoslavia in the early 1990s, or Rwanda in 1994. But the one I keep coming back to is Lebanon in the 1970s and 1980s. The Lebanese civil war was interesting because it pitted dozens of individual factions against each other in constantly shifting alliances with many factions doubling as organized crime groups. The breakdown in Lebanon was mostly along religious lines with Sunni, Shia, Maronites, Druze, and Alawites plus ethnic Armenians, Palestinians, and Communists all fighting each other, and with persistent involvement by the Israelis, Syrians, Iranians, Americans, and Europeans.
I suspect America’s Civil War Two (which hopefully will not happen) would be similar. The USA is roughly 50 times the size of Lebanon in terms of population and geography. It is likely a US civil war would involve dozens if not hundreds of factions at the local, regional, and national level, including the military, police, defectors from state security forces, organizations of the deep state, alphabet soup agencies, far-left and far-right groups of many different varieties, ethnic and religious factions, cults, civilian vigilantes and self-defenders, gangs, militias, and foreign fighters. Not a pleasant situation.
The Lebanese Civil War (Arabic: الحرب الأهلية اللبنانية, romanized: Al-Ḥarb al-Ahliyyah al-Libnāniyyah) was a multifaceted civil war in Lebanon, lasting from 1975 to 1990 and resulting in an estimated 120,000 fatalities. As of 2012, approximately 76,000 people remain displaced within Lebanon. There was also an exodus of almost one million people from Lebanon as a result of the war.
Before the war, Lebanon was multi-sectarian, with Sunni Muslims and Christians being the majorities in the coastal cities, Shia Muslims being mainly based in the south and the Beqaa Valley to the east, and with the mountain populations being mostly Druze and Christian. The government of Lebanon had been run under a significant influence of the elites among the Maronite Christians. The link between politics and religion had been reinforced under the mandate of the French colonial powers from 1920 to 1943, and the parliamentary structure favored a leading position for its Christian population. However, the country had a large Muslim population and many pan-Arabist and left-wing groups opposed the pro-western government. The establishment of the state of Israel and the displacement of a hundred thousand Palestinian refugees to Lebanon during the 1948 and 1967 exoduses contributed to shifting the demographic balance in favor of the Muslim population. The Cold War had a powerful disintegrative effect on Lebanon, which was closely linked to the polarization that preceded the 1958 political crisis, since Maronites sided with the West while leftist and pan-Arab groups sided with Soviet-aligned Arab countries.
Fighting between Maronite and Palestinian forces (mainly from the Palestine Liberation Organization) began in 1975, then Leftist, pan-Arabist and Muslim Lebanese groups formed an alliance with the Palestinians. During the course of the fighting, alliances shifted rapidly and unpredictably. Furthermore, foreign powers, such as Israel and Syria, became involved in the war and fought alongside different factions. Peacekeeping forces, such as the Multinational Force in Lebanon and the United Nations Interim Force in Lebanon, were also stationed in Lebanon.